1. Field of the Invention
The present invention relates to a television receiver which permits a viewer to simultaneously watch a main picture and a sub-picture, and more particularly, to a device for processing a sub-picture for such a television.
2. Background of the Related Art
As the technology in television (TV) advances, a TV system which permits a viewer to simultaneously watch both a main picture and a sub-picture has been developed. For example, if a scene of a decoded main picture and a decoded sub-picture is as shown in FIG. 1, a simultaneous display of the main picture and the sub-picture according to a Picture In Picture (PIP) function is as shown in FIG. 2.
The sub-picture may be used to search for another channel. Thus, when the sub-picture covers an important part of the main picture, the sub-picture may be moved to another position. However, the sub-picture must at times be turned on and off because the movement of the sub-picture is limited. Also, a size of the sub-picture display can be reduced, but there too is a limitation of the size reduction. As a result, the PIP function may be cumbersome to a viewer.
Typically, the sub-picture as shown in FIG. 3A is respectively sub-sampled by 1/N and 1/M in width and length, i.e. one line is taken out of M vertical lines and one line is taken out of N horizontal lines, to become the sub-picture as shown in FIG. 3B. Therefore, displaying only a portion of the sub-sampled sub-picture requires sub-sampling of all regions of the received sub-picture, storing the receives sub-picture in a frame memory, and reading only the portion to be displayed. Thus, complicated logics, such as a multiplier for addressing, is necessary.
Accordingly, an object of the present invention is to solve at least the problems and disadvantages of the related art.
An object of the present invention is to provide a device for processing a sub-picture, which permits a free movement of the sub-picture on a main picture.
Another object of the present invention is to provide a device for processing a sub-picture, which permits a free adjustment of the sub-picture size.
A further object of the present invention is to provide a device for processing a sub-picture, which displays a portion of the sub-picture by a simple memory indexing.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the device for processing a sub-picture in a TV receiver includes a PIP synchronizing generator for receiving an input signal from an external device, receiving a main picture synchronizing signal, and generating information on a PIP; a read timing generator for generating a read signal from a synchronizing signal for displaying the sub-picture generated at the PIP synchronizing generator; a write timing generator for generating a write signal by using the sub-picture synchronizing signal and an output of the PIP synchronizing generator; a sub-sampler for selecting and sub-sampling only a portion of the sub-picture data to be displayed, the sub-picture data being provided in response to the write signal from the write timing generator; a sub-picture frame memory for storing the sub-picture data sub-sampled at the sub-sampler and presenting the stored sub-picture data in response to the read signal generated at the read timing generator; and a multiplexer for multiplexing the decoded main picture data and the sub-picture data read from the sub-picture frame memory.
The PIP synchronizing generator generates the synchronizing signals for lines of the sub-picture to be displayed on the main picture, and a signal representing a line counted from a top side of the sub-sampled sub-picture to which the sub-picture is not to be displayed and a number of lines to be displayed, using the information on sub-picture vertical starting point coordinates, sub-picture length and main picture line. The synchronizing signals for the lines of the sub-picture to be displayed on the main picture are activated at lines on which the sub-picture is displayed.
Also, the PIP synchronizing generator generates synchronizing signals for columns of the sub-picture to be displayed on the main picture, and a signal representing a pixel counted starting from a left most side of the sub-sampled sub-picture up to which the sub-picture is not to be displayed and a number of pixels per line to be displayed, using the information on sub-picture horizontal starting point coordinates, a sub-picture width and main picture column. The synchronizing signals for columns of the sub-picture to be displayed on the main picture are activated on columns at which the sub-picture is displayed.